Summary: Potomavax is a Vaccine used in horses to aid in prevention of Equine Potomac Horse Fever (A.K.A neorickettsiosis) is caused by Ehrlichia risticii.
Potomac horse fever (PHF) is a disease that affects horses during warm weather months, occasionally causing outbreaks of diarrheal illness in horses that are kept near rivers, streams, or in irrigated pastures.
The bacterium responsible for the disease, Neorickettsia risticii, has an unusual history: it has been identified in flukes (flatworms) that develop in aquatic snails. When the water warms up during the summer, infected immature flukes, called cercariae, are released from the snails into the aquatic environment. These immature flukes can be swallowed by horses drinking from rivers or streams, but, more commonly, they are picked up by aquatic insects such as caddisflies, mayflies, damselflies, and dragonflies, where they develop into their next life stage, metacercariae. Infected aquatic insects such as the caddisflies and mayflies, which can hatch in mass, also might carry the organism to horses to pick up as they graze.
The currently available commercial vaccine is a killed, adjuvanted product, which is also available combined with rabies vaccine. The current vaccine does not carry a label claim for the prevention of abortion.
DOSAGE (Labelled Dosage): For primary vaccination, aseptically inject 1 mL (1 dose) intramuscularly into healthy horses 3 months of age or older. Revaccinate with a second 1 mL dose 3 to 4 weeks later. Revaccinate annually with a single 1 mL dose.
PRECAUTIONS: Store at 2-7°C (35-45°F). Do not freeze. Use entire contents when first opened. Shake well before using. Contains gentamicin as a preservative. Do not vaccinate within 21 days prior to slaughter. In rare instances, administration of vaccines may cause lethargy, fever, and inflammatory or hypersensitivity types of reactions. Treatment may include antihistamines, anti-inflammatories, and/or epinephrine. Vaccinating animals whose immune response is compromised by stress, disease, etc. may not produce the desired results.
Vaccination Schedules(AAEP Vaccine Recommendations):
Due to the seasonal incidence of disease, vaccination should be timed to precede the anticipated peak challenge during the summer months or fall.
Adult horses, previously vaccinated: Manufacturers recommend revaccination at 6- to 12-month intervals. However, veterinarians may consider an interval of 3 to 4 months for horses in endemic areas because protection following vaccination can be incomplete and short-lived.
Adult horses, previously unvaccinated or with unknown vaccinal history: Administer a primary series of 2 doses, at a 3- to 4-week interval. Peak protection occurs 3 to 4 weeks after the second dose.
Pregnant mares previously vaccinated against PHF: Vaccinate semi-annually to annually. Schedule 1 dose to be administered 4 to 6 weeks before foaling. To date no studies have been published that examine the efficacy of PHF vaccines to prevent N. risticii induced abortion.
Pregnant mares unvaccinated or with unknown vaccinal history:Administer a primary series of 2 doses, at a 3- to 4-week interval. Schedule so that 2nd dose is administered 4 to 6 weeks before foaling.
Foals: Due to the low risk of clinical disease in young foals and the possible maternal antibody interference, primary immunization for most foals can begin after 5 months of age. The manufacturer’s recommendation is for a 2-dose series administered at a 3 to 4 week interval. However, as with other killed products, a third dose at 12 months of age is recommended. If the primary series is initiated when foals are less than 5 months of age, additional doses should be administered at monthly intervals up to 6 months of age to ensure that an immunologic response is achieved.
Horses having been naturally infected and recovered: Administer a primary series (as described above) or booster vaccine (if previously vaccinated) 12 months following recovery from natural infection.
USEF Regulation: None except 12 hour injections rule.
Returns: Vaccines cannot be returned.